AHA, BHA and PHA: Choosing the Right Exfoliant
Three families, one spectrum
Chemical exfoliants get grouped together and used interchangeably, which is how people end up irritated. They are not interchangeable. The difference is molecule size and solubility, and that difference decides where in the skin each one works.
PHA, gluconolactone, lactobionic acid, has the largest molecule. It stays near the surface, works slowly, and holds water while it does. The mildest of the three.
AHA, glycolic, lactic, mandelic, works on surface texture and tone. Water-soluble, so it does not travel into the pore.
BHA, salicylic acid, is oil-soluble. That is the whole point: it is the only one of the three that gets inside a pore and clears what is sitting there.
Which one for your concern
Blackheads and congestion. BHA, because nothing else reaches the problem. Look for it in toners and pads rather than rinse-off cleansers, contact time matters more than concentration here.
Rough texture, dull tone. AHA. Pairs well with niacinamide for tone work, and with tranexamic acid if you are treating marks.
Sensitive or dry skin. PHA. It exfoliates slowly enough that reactive skin keeps up, and the humectant effect means it does not leave skin tight.
How Korean formulas differ
Western acid products often run high concentrations for weekly use. Korean formulas typically use lower strengths in toners and pads designed for daily or near-daily application. Neither approach is wrong, but they ask different things of you: one is an event, the other is a habit.
The low-strength daily approach tends to suit more people, because the barrier never takes a large hit. It also pairs better with centella-based formulas, which is why so many Korean acid pads include it.
How often is too often
Two to three times a week for most skin. Daily only if the formula is specifically built for it, and even then, watch for the signals: tightness after cleansing, a shiny-red look, products that suddenly sting. Those mean stop, not push through.
If you have crossed that line, stop exfoliating entirely. Run barrier repair, centella, ceramides, hyaluronic acid, for two weeks, then reintroduce at half your previous frequency.
What not to combine
Not acids and retinoids on the same night, at least while you are starting out. Alternate evenings. Experienced skin sometimes handles both, but there is no real advantage in rushing there.
And after exfoliating, sun protection is not optional. Freshly exfoliated skin burns faster, and burning undoes exactly what you were exfoliating for.
Where to start
Congestion: a BHA pad or toner, three nights a week. Texture: an AHA at low strength. Sensitive skin: PHA, daily. The full range is in our AHA, BHA and PHA collection, and pore tightening covers the wider routine.